The Food Lab: How to Make Tonkotsu Ramen Broth at Home

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[Photographs: J. Kenji Lopez-Alt]

Like most of you guys out there, the ramen of my youth was served in two discrete serving sizes: by the Cup, or by the Oodle. The noodles were soft and squiggly, the broth was thin and salty, the corn was de-hydrated then re-hydrated, and the scallions were, well, at least they were green. Despite all these shortcomings, the stuff was still a tasty meal, and I don't mean give-in-because-there's-nothing-better tasty in the "I guess I'll go watch Star Wars Episode I in the theaters yet again," kind of way,* but must-eat-tasty in the "Holy Cow! Empire Strikes Back is playing on the big screen for one showing only, I gotta get me some of that!" kind of way.

*Damn you, George Lucas, for continually finding new ways to make me poorer and you richer thirteen bucks at a time. You're almost as good as Paul McCartney at this game!

Imagine my elation, then, several years later when I found out that Cup Noodles are not the be-all end-all to ramen. I can't remember the first place I tried real-deal freshly-made ramen (most likely it was at a nondescript Ramen-ya in New York with my grandmother), but I definitely remember the effect it had on me. Tasting it was like suddenly discovering the wood-fired glory of Motorino's pizza after living off of frozen Elio's for my whole life. It wasn't just a game-changer—it outright altered the basic rules of physics.

Since then, I've been a man obsessed, eating ramen at nearly every ramen-ya in New York, and throughout different regions of Japan. Heck, I even gave a talk about ramen at the Japan Society once with the founders of the Ramen Museum in Yokohama. My love for ramen has driven me all around the world and more than once has tested the strength of my marriage.*

*Don't worry, our love always manages to bounce back like a good alkaline noodle

Just as with pizza, the regional variation between bowls of ramen—the broth, the flavoring, the toppings, and the noodle style—are staggering, but there's no doubt in my mind that the King of Slurpdom, the Pope of Noodle Town, the broth cut from a different cloth, the bowl with the most soul is tonkotsu ramen.

Made with an intensely porky, opaque pale broth with a sticky-lipped intensity and the rich, buttery texture of light cream, there's no smell more warming on a cold day than a big hot bowl of tonkotsu ramen set before you. The best sport tiny nubbins of fat swimming around on their surface, a slick of mayu (black garlic oil) or chile-sesame paste, a handful of thin-sliced green onions, a soft-yolked soy-sauce tinged egg, and a few slices of meltingly tender cha siu pork belly. It's the ultimate meal-in-a-bowl and what any Japanese business man or woman—and a good deal of Americans these days—thinks of the moment you mention comfort food.

As a New York resident, I've got it easy when it comes to finding good ramen (check out our guide to the best here). But cities change, people move, and I've got my less fortunate friends and family to think of.

The challenge? Figure out how to make world-class tonkotsu ramen right in my own kitchen. It took over 40 pounds of bones and over 200 hours of collective simmering time to do it, but I cracked the code. Luckily, the wife was out of the country for a week.

simmer-fest

Bones To Pick

Having been trained in classical Western kitchens, my first instinct when making a broth is to keep it as clean as possible. Perfect clarity is the goal. As Michael Ruhlman puts it, you want to be able to read the date on a penny at the bottom of a pot of good French stock. To achieve this, you boil your bones and aromatics as gently as possible—a sub-simmer, with the surface barely quivering—meticulously straining the entire time to remove any impurities that might cloud your soup.

When making a Western-style stock, heating bones in water is a means of removing water-soluble proteins from the interior and exterior of the bones and dissolving them into solution, adding flavor to the water. The heating and simmering process also catalyzes a few other reactions, mainly the conversion of collagen—the protein that comprises most of the connective tissue—into gelatin, the familiar protein that thickens and adds richness to broth (and Jell-O).

With tonkotsu broth, on the other hand, you go one step further. In this case, bones are cooked at a rolling boil for a long, long, long, long period of time. Not only does all the same dissolving and gelatin creation take place, but you also end up breaking down other matter—fat, marrow, calcium, various other minerals and proteins—into tiny tiny pieces which get suspended in the liquid, turning it opaque.

So how long does this process take? I've read reports ranging anywhere from an hour and a half in a pressure cooker up to 60 hours at a low boil on a stove-top.

Putting on the Pressure

Being a man who is lazy by nature, I decided to try the quick, hour-and-a-half pressure cooker method first, using a combination of split pork trotters (they boast plenty of flavor, lots of collagen, and a good amount of fat and marrow—I found that getting them cut into cross-wise disks rather than split lengthwise makes for better extraction) and a chicken carcass to mellow out the flavor.

What emerged from the pressure cooker sure was tasty, but it was by no means a good tonkotsu ramen broth. Rich with gelatin and flavor, to be sure, but it was nearly transparent in color. The problem is that in the high-pressure environment of a pressure cooker, temperatures get higher, allowing for fast extraction and conversion of collagen to gelatin, but the high pressure also prevents the rolling boil necessary for getting those extracted solids to emulsify into the broth.

A Matter of Time

Next, I cooked a batch the traditional way—on the stovetop in a regular Dutch oven, pulling out ladlefuls of broth at thirty minute intervals and chilling them in the fridge (to get a better gauge of the broth's progress).

I was curious as to how the matter that causes the broth to turn milky white actually gets suspended in the water. We all know that fat tends to coalesce and float to the top of a broth while particulate matter can sink or float depending on its density, right? Well, my theory is that in the case of tonkotsu broth, the gelatin created as the broth cooks acts as a kind of net, trapping all that good stuff and causing the broth to become both opaque, and more flavorful. If this is true, we should begin to see the broth turning opaque at around the same time as enough collagen converts to gelatin to significantly thicken it.

Here's what I saw:

After 1 hour: the broth is pale and watery. Very little flavor has developed and there is no gelatin formation to speak of.

After 2 hours: there is significantly more flavor development, though still only minimal gelatin formation. Straight from the fridge the broth has a tiny bit of body. Let it warm up at room temp for a minute or two, and it's completely liquid. No opaque milkiness yet, implying that very few minerals or fats are emulsified into the liquid.

After 4 hours: a great deal of the collagen from the pig's trotters has converted to gelatin, creating a broth that remains as a loose gel even at room temperature. Right on cue, the broth also starts to look opaque. At this point, you can't see anything beyond the top half-inch of liquid. The aroma is rich and deep, but the broth is also quite dark, which is a little troublesome—pale off-white is what we're after.

After 6 hours Our broth is solid enough when chilled that you can pick it up in soft-ball sized chunks without it breaking or slipping through your fingers. It's also extremely cloudy at this point—you have trouble seeing anything hiding just below the surface.

After 12 hours we see a broth thickened to pretty much its maximum. The pig's trotters have completely disintegrated leaving little but bone and a few scraps of soft skin here and there. The rest has melted completely into the broth. While there is change between 6 and 12 hours, it's not nearly as significant as in the earlier stages. Continuing to cook the broth past this point (I went up to 48 hours before calling it a day) afforded no noticeable advantages.

So far, I think the theory of gelatin helping to suspend cloudy particulate matter is a sound one, but I had a much bigger problem on my hands:

The broth is brown.

In Western cuisine, if you want a brown broth, you have to roast your bones first. Roasting creates brown colors, and those colors get transferred to your broth. I didn't roast my bones, so why was my broth turning brown? Obviously there's something else

Blood Bath

Watching a little more closely as the bones heat up reveals the answer:

In the early stages, while the water is still too cold to actually start cooking the bones, but while there's still enough to allow the bones to start giving up their goods, you'll notice that the water turns a pale pink from the pigments coming out of them (a combination of hemoglobin—the pigment that colors blood—and myoglobin—the analogous pigment for muscle tissue). Continue to cook, and the color appears to go away, but in reality, it's merely lurking in the shadows, waiting for time, concentration, and oxygen to do their work, transforming them into deep brown pigments.

The only way to get rid of them? Wash those bones, and wash'em well.

The best way to do this is to cover the bones with cold water and bring the whole pot to a boil, allowing the blood vessels and muscle fibers to tighten up and begin squeazing out their unwanted contents (this stuff, by the way, is what you are skimming away when making a French stock). As soon as the water comes to a boil, dump the entire contents into the sink.

Isn't that fun? If you're the kind of person who always enjoy squeezing blemishes or popping blisters (I know several folks like this, including both family members and spouses!), the next step will be right up your alley.

Your mission, should you choose to accept it: remove every last bit of brown-tinted anything from all the bones. This means blood, bits of organ, dark marrow, anything that's not beige or white needs to be removed. Cold running water and a chopstick help. It's a sort of time-consuming process, but it's a good way to zen out for fifteen minutes and contemplate the meaning life, death, and noodles.

This is what stock made from un-cleaned bones looks like after about 20 minutes on the stovetop:

Ugly, right?

Once I restarted my stock with completely cleaned bones, I got none of that. Or at least, very little of it. Most of the gunk and scum manifested itself within the first 20 minutes as a few rogue bits of flotsam which were easily skimmed off, as well as a bit of debris that clung to the sides of the Dutch oven—easy to wipe off with a sponge or moist paper towel.

Was it worth it in the end?

Here's the broth I ended up with after 10 hours of cooking:

And here are the two broths side-by-side.

Remember, these two broths are completely identical save for the fact that the broth on the right was made from blanched-then-washed bones, while the broth on the left was made from completely fresh bones. Both were packed with flavor, both were rich, thick, opaque, and gelatinous, but only the washed bones delivered the clean color I was looking for.

Back To Fat

At this point, I could have thrown in the side-towel and called it a day. After all, many ramen-ya get along just fine with tonkotsu broth, flavorings, noodles, and toppings. But sorry, not good enough for me.

See, the best of the best, cream of the crop ramen-ya will add a final little flourish to push their bowls of soup over into top-ramen territory: finely chopped, super-tender pork fat.

To get it is simply a matter of adding a hunk or pork fatback (the fresh, not salted kind) directly to your pot as the bones cook. After the first four hours or so, you end up with fat that is almost liquid in texture but still manages to barely hold its shape, like the finest panna cotta.

I chopped this fat up into tiny bits then whisked some into the soup just before serving with a vigorous hand to break up the bits even further.

The fat is there, to be sure—you can see the little bits floating around on top—but it's so tender that you don't feel it on your tongue. Instead, you simply get an unparalleled feeling of rich meatiness. If you could convert the world's juiciest, fattiest pork chop into slurpable, liquid form, that's what you get with each bite of the fat-laced broth.

Amping Up Umami

With the broth and fat out of the way, I turned my attention towards fine-tuning the aromatics. Up to now, I'd been using a simple combination of raw onions, garlic, and ginger, but there was something missing. The sweet-pungent combination that alliums provide always goes well with pork, so I decided to add a couple leeks as well as some scallion whites (I'd save the greens for garnish) to my broth.

What about charring? I knew that both the Maillard reaction and caramelization—the respective browning reactions that occur when proteins or sugars are heated—can add complexity and create new flavor compounds that can boost the umami-factor of a dish (that's the Japanese word for savory), so I decided to cook down my onions, garlic, and ginger before adding them to the broth (I left the leeks and scallions raw to maintain a bit of mild raw onion flavor). I realized that in this case, the browner the better—cooking the onions, garlic, and ginger until nearly black was the way to go.

Scanning around the fridge, my normal go-to umami bombs—anchovies and marmite—seemed out of place in this context, but a container of mushroom trimmings I had saved was an ideal flavor booster (you can use whole mushrooms if you wish).

Japanese ramen soup is made with two distinct parts—the broth, and the flavoring. The former can be anything from a light seafood-based dashi broth, a rich chicken broth, or a thick, creamy tonkotsu broth like we've made here. The latter is most commonly sea salt, soy sauce, or miso, though any number of additional seasonings—sesame paste, chili oil, or muyu—can be added to enhance or complement the flavor of the broth. In this case, I went with salt, a splash of good aged soy sauce, and a little drizzle of sesame-chili oil.

After a dozen-odd hours of boiling and waiting, there's something cathartic about pouring a few hot ladles of broth over a steaming bowl of noodles. You feel a connection to this little bowl like no other. It's come a long way with you from its early, clumsy little steps to its current, fully fleshed-out form, and you've grown right a long with it. It's almost a shame you have to eat it, and I can't help but feel a bit like Homer eating Mr. Pinchy when I dig in.

Served with plenty of scallions, bouncy noodles, a perfectly soft-boiled marinated egg, and a few slices of sweet, melt-in-you-mouth-tender pork belly cha siu, you couldn't ask for a more satisfying meal to eat—or to make, for that matter.

Wait, what's that you say? You don't have the recipe for bouncy ramen noodles, bitter-sweet mayu, or meltingly tender cha siu pork?

Well, we've got to leave a few tricks up our sleeve for next week, right?

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About the Author

J. Kenji López-Alt is the Managing Culinary Director of Serious Eats, and author of the James Beard Award-nominated column The Food Lab, where he unravels the science of home cooking. A restaurant-trained chef and former Editor at Cook's Illustrated magazine, he is the author of upcoming The Food Lab: Better Home Cooking Through Science, to be released by W. W. Norton.

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